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Magnetic In x Ga 1 - x N nanowires at room temperature using Cu dopant and annealing.

Park YH, Ha R, Park TE, Kim SW, Seo D, Choi HJ - Nanoscale Res Lett (2015)

Bottom Line: The typical diameter of the Cu:In x Ga1 - x N nanowires was 80 to 150 nm, with a typical length of hundreds of micrometers.The as-grown nanowires exhibited diamagnetism.After annealing, the nanowires exhibited ferromagnetism with saturation magnetic moments higher than 0.8 μB (1 μB × 10(-24) Am(2)) per Cu atom at room temperature by the measurements using a superconducting quantum interference device (SQUID) magnetometer.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, Yonsei University, Seoul, 120-749, Republic of Korea, younhopark@yonsei.ac.kr.

ABSTRACT
Single-crystal, Cu-doped In x Ga1 - x N nanowires were grown on GaN/Al2O3 substrates via a vapor-liquid-solid (VLS) mechanism using Ni/Au bi-catalysts. The typical diameter of the Cu:In x Ga1 - x N nanowires was 80 to 150 nm, with a typical length of hundreds of micrometers. The as-grown nanowires exhibited diamagnetism. After annealing, the nanowires exhibited ferromagnetism with saturation magnetic moments higher than 0.8 μB (1 μB × 10(-24) Am(2)) per Cu atom at room temperature by the measurements using a superconducting quantum interference device (SQUID) magnetometer. X-ray absorption and X-ray magnetic circular dichroism spectra at Cu L 2,3-edges indicated that the doped Cu had a local magnetic moment and that its electronic configuration was mainly 3d (9). It possessed a small trivalent component, and thus, the n-type behavior of electrical property is measured at room temperature.

No MeSH data available.


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AXS spectra at the CuL2,3-edge and XMCD data. (a) AXS spectra at the Cu L2,3-edge for Cu-doped InxGa1 - xN measured at 300 K. The inset shows the AXS spectra at the Cu L2,3-edge for reference CuO powder. (b) XMCD data showing the difference between the Cu L2,3-edge AXS spectra for the different spin directions (ρ+ and ρ-) of nanowires measured at 300 K.
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Fig3: AXS spectra at the CuL2,3-edge and XMCD data. (a) AXS spectra at the Cu L2,3-edge for Cu-doped InxGa1 - xN measured at 300 K. The inset shows the AXS spectra at the Cu L2,3-edge for reference CuO powder. (b) XMCD data showing the difference between the Cu L2,3-edge AXS spectra for the different spin directions (ρ+ and ρ-) of nanowires measured at 300 K.

Mentions: To investigate whether Cu dopants are incorporated in the crystalline lattice of InxGa1 - xN nanowires or not, we measured AXS for the InxGa1 - xN nanowires around the Cu K absorption edge. Figure 3a shows the L-edge absorption spectra for Cu-doped InxGa1 - xN nanowires. The absorption spectrum peaks are separated into two regions of L3 and L2, due to the spin-orbit split of the core levels. This is consistent with the well-known 930- to 931-eV peak of CuO corresponding to the 3d9 ground state (2p to 3d dipole transition)[11]. The Cu absorption spectrum peak and the largest peak for Cu-doped InxGa1 - xN nanowires are located at the same energy of 930 eV for the 3d9 ground state of CuO. There is also another identical but smaller peak at an energy level that is 3.5 eV higher. There is no such corresponding peak in divalent (2+) or monovalent (1+) Cu compounds[19, 20]. It is common in the AXS spectra that higher valence states of 3d transition metals appear at energies that are higher by 2 to 4 eV because of the decreased Coulomb energy between the core hole and valence electrons of the final state[21–23]. Accordingly, we expected that it is related to the trivalent (3+) state. The identical line structure is reproduced at the L2 region[19, 20]. It is thus confirmed that the electronic configuration of doped Cu is mainly 3d9. The formal ionic valence of Cu at cation sites is trivalent; however, it seems that the locally divalent state is preferred for covalent bonding with nitrogen. This suggests that the ionocovalent bonding nature of the Cu 3d orbital with the surrounding semiconductor medium provides the Cu atom with a mixed electron configuration.Figure 3


Magnetic In x Ga 1 - x N nanowires at room temperature using Cu dopant and annealing.

Park YH, Ha R, Park TE, Kim SW, Seo D, Choi HJ - Nanoscale Res Lett (2015)

AXS spectra at the CuL2,3-edge and XMCD data. (a) AXS spectra at the Cu L2,3-edge for Cu-doped InxGa1 - xN measured at 300 K. The inset shows the AXS spectra at the Cu L2,3-edge for reference CuO powder. (b) XMCD data showing the difference between the Cu L2,3-edge AXS spectra for the different spin directions (ρ+ and ρ-) of nanowires measured at 300 K.
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Fig3: AXS spectra at the CuL2,3-edge and XMCD data. (a) AXS spectra at the Cu L2,3-edge for Cu-doped InxGa1 - xN measured at 300 K. The inset shows the AXS spectra at the Cu L2,3-edge for reference CuO powder. (b) XMCD data showing the difference between the Cu L2,3-edge AXS spectra for the different spin directions (ρ+ and ρ-) of nanowires measured at 300 K.
Mentions: To investigate whether Cu dopants are incorporated in the crystalline lattice of InxGa1 - xN nanowires or not, we measured AXS for the InxGa1 - xN nanowires around the Cu K absorption edge. Figure 3a shows the L-edge absorption spectra for Cu-doped InxGa1 - xN nanowires. The absorption spectrum peaks are separated into two regions of L3 and L2, due to the spin-orbit split of the core levels. This is consistent with the well-known 930- to 931-eV peak of CuO corresponding to the 3d9 ground state (2p to 3d dipole transition)[11]. The Cu absorption spectrum peak and the largest peak for Cu-doped InxGa1 - xN nanowires are located at the same energy of 930 eV for the 3d9 ground state of CuO. There is also another identical but smaller peak at an energy level that is 3.5 eV higher. There is no such corresponding peak in divalent (2+) or monovalent (1+) Cu compounds[19, 20]. It is common in the AXS spectra that higher valence states of 3d transition metals appear at energies that are higher by 2 to 4 eV because of the decreased Coulomb energy between the core hole and valence electrons of the final state[21–23]. Accordingly, we expected that it is related to the trivalent (3+) state. The identical line structure is reproduced at the L2 region[19, 20]. It is thus confirmed that the electronic configuration of doped Cu is mainly 3d9. The formal ionic valence of Cu at cation sites is trivalent; however, it seems that the locally divalent state is preferred for covalent bonding with nitrogen. This suggests that the ionocovalent bonding nature of the Cu 3d orbital with the surrounding semiconductor medium provides the Cu atom with a mixed electron configuration.Figure 3

Bottom Line: The typical diameter of the Cu:In x Ga1 - x N nanowires was 80 to 150 nm, with a typical length of hundreds of micrometers.The as-grown nanowires exhibited diamagnetism.After annealing, the nanowires exhibited ferromagnetism with saturation magnetic moments higher than 0.8 μB (1 μB × 10(-24) Am(2)) per Cu atom at room temperature by the measurements using a superconducting quantum interference device (SQUID) magnetometer.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, Yonsei University, Seoul, 120-749, Republic of Korea, younhopark@yonsei.ac.kr.

ABSTRACT
Single-crystal, Cu-doped In x Ga1 - x N nanowires were grown on GaN/Al2O3 substrates via a vapor-liquid-solid (VLS) mechanism using Ni/Au bi-catalysts. The typical diameter of the Cu:In x Ga1 - x N nanowires was 80 to 150 nm, with a typical length of hundreds of micrometers. The as-grown nanowires exhibited diamagnetism. After annealing, the nanowires exhibited ferromagnetism with saturation magnetic moments higher than 0.8 μB (1 μB × 10(-24) Am(2)) per Cu atom at room temperature by the measurements using a superconducting quantum interference device (SQUID) magnetometer. X-ray absorption and X-ray magnetic circular dichroism spectra at Cu L 2,3-edges indicated that the doped Cu had a local magnetic moment and that its electronic configuration was mainly 3d (9). It possessed a small trivalent component, and thus, the n-type behavior of electrical property is measured at room temperature.

No MeSH data available.


Related in: MedlinePlus